fix links to stac-api repo

Author: philvarner

README.md

@@ -4,18 +4,18 @@
 - **Conformance Classes:** 
   - `STAC API - Item Search` binding: <https://api.stacspec.org/v1.0.0-rc.1/item-search#fields>
   - `STAC API - Features` binding: <https://api.stacspec.org/v1.0.0-rc.1/ogcapi-features#fields>
-- **Extension [Maturity Classification](https://github.com/radiantearth/stac-api-spec/blob/main/README.md#maturity-classification):** Candidate
+- **Extension [Maturity Classification](https://github.com/radiantearth/stac-api-spec/tree/v1.0.0-rc.1/README.md#maturity-classification):** Candidate
 - **Dependencies:**
-  - [STAC API - Item Search](https://github.com/radiantearth/stac-api-spec/blob/main/item-search)
-  - [STAC API - Features](https://github.com/radiantearth/stac-api-spec/blob/main/ogcapi-features)
+  - [STAC API - Item Search](https://github.com/radiantearth/stac-api-spec/tree/v1.0.0-rc.1/item-search)
+  - [STAC API - Features](https://github.com/radiantearth/stac-api-spec/tree/v1.0.0-rc.1/ogcapi-features)
 
 STAC API by default returns every attribute in an item. However, Item objects can have hundreds of fields, or incredibly large
 geometries, and even smaller Item objects can get big when millions are requested but not all information is used. This
 fragment provides a mechanism for clients to request that servers to explicitly include or exclude certain fields.
 
 This fragment may be bound to either or both of 
-[STAC API - Item Search](https://github.com/radiantearth/stac-api-spec/blob/main/item-search) (`/search` endpoint) or
-[STAC API - Features](https://github.com/radiantearth/stac-api-spec/blob/main/ogcapi-features) (`/collections/{collectionId}/items` endpoint) by
+[STAC API - Item Search](https://github.com/radiantearth/stac-api-spec/tree/v1.0.0-rc.1/item-search) (`/search` endpoint) or
+[STAC API - Features](https://github.com/radiantearth/stac-api-spec/tree/v1.0.0-rc.1/ogcapi-features) (`/collections/{collectionId}/items` endpoint) by
 advertising the relevant conformance class. 
 
 When used in a POST request with `Content-Type: application/json`, this adds an attribute `fields` with 
@@ -44,7 +44,7 @@ support the EO Extension, a successful HTTP response must be returned and the It
 attribute. 
 
 If no `fields` are specified, the response is **must** be a valid
-[ItemCollection](https://github.com/radiantearth/stac-spec/blob/main/itemcollection/README.md). If a client excludes
+[ItemCollection](https://github.com/radiantearth/stac-spec/tree/v1.0.0-rc.1/itemcollection/README.md). If a client excludes
 attributes that are required in a STAC Item, the server may return an invalid STAC Item. For example, if `type` 
 and `geometry` are excluded, the entity will not even be a valid GeoJSON Feature, or if `bbox` is excluded then the entity 
 will not be a valid STAC Item.